Saliva tests detect disease, cavities and drug use
Photo credit: Monica Amarelo
Researchers at the 2005 AAAS Annual Meeting in Washington, D.C, said today that a saliva-based diagnostic is evolving to test for bacteria, viruses, illegal drug use, steroids, antibodies, DNA and RNA, potentially reducing the need for blood and urine testing.
"Saliva is a reflection of our body, our circulation and our blood," Dr. David Wong of the University of California, Los Angeles, and the Jonsson Cancer Center, told reporters at a AAAS news briefing.
Saliva testing can be effective because it contains many of the same proteins that blood and urine do, the researchers said. New research shows these molecules can reveal the presence of diseases like cancer, and can be used to predict the number of cavities in a person's teeth.
While some saliva tests are already in use for alcohol and HIV tests, new technology has overcome barriers to build a new generation of precise portable saliva-testing devices that reconfigure tests normally done with blood and urine.
Dr. David Wong of the University of California-Los Angeles Jonsson Cancer Center and School of Dentistry is leading an effort to decipher the set of proteins, or "proteome," present in saliva.
"If we could index all the proteins in saliva into a catalog for healthy people, then we could compare it with the salivary proteome of the diabetic population, for example," Wong said.
He estimated that it will take about two years to complete the saliva roadmap and then researchers can begin to look for signatures to detect diabetes, rheumatoid arthritis, and other diseases.
"There are a dozen companies that make the oral fluid test for HIV worldwide, but only one has been approved in the U.S.," said Daniel Malamud, a professor in the Department of Biochemistry at the School of Dental Medicine at the University of Pennsylvania.
Malamud revealed a prototype oral swab kit that detects HIV and Bacillus cereus, a bacterium closely related to B. anthracis. He believes the device will lead to a palm-sized kit which could detect exposure to a variety of substances, from narcotics to steroids to common bacteria and viruses. The miniaturized lab will permit saliva screening on the go.
"Scientists have already developed a means of analyzing oral fluid samples for blood alcohol, HIV antibodies and steroid hormones using a swab test," said Malamud. "The next step is to develop a method to detect and identify DNA, bacteria or viruses."
Malamud stressed the importance of technology that can be used right in the doctor's office. For example, doctors often put children with respiratory infections on antibiotics until they get their test results. If a diagnosis from a saliva test were available right away, it could prevent unnecessary use of antibiotics, which can lead to bacterial resistance.
Paul Denny, a researcher from the University of Southern California and Proactive Oral Solutions, dreams of generating a battery of wellness tests to monitor "when the body is doing things right, and not just when things go wrong."
Oral fluid testing also can determine how vulnerable the patient is to cavities. Denny's research found a relationship between saliva proteins and caries, or tooth decay, which suggests this simple saliva test can predict whether children will develop cavities, how many cavities they will develop and even which teeth are most vulnerable.
"Everyday there is a new mystery that is unraveled, giving us a better idea of how to refine tolerances so we have a long, healthy lifestyle," said Denny. "With children, it becomes a prescription for prevention. Test results will forecast the caries history of baby teeth in children. The test will predict what the future oral health care needs of that child may be."
The saliva test's ability to pinpoint the vulnerability of specific teeth can reduce the cost and increase the effectiveness of a prevention plan. This test has important public health implications in areas where families cannot afford routine dental exams.
"This is an exciting time for molecular diagnostics," said Wong. "Saliva tests can provide early detection of oral cancer. Early detection of other diseases is another question, but results are promising and we are hopeful that is the next step."
There is a national agenda by the National Institute of Dental and Craniofacial Research[link: http://www.nidcr.nih.gov] to bring saliva diagnostics to fruition. There are 10 groups funded by the institute to bring saliva diagnostics into the forefront.
Saliva testing is already being used in the workplace, for drug testing, said Edward Cone, president and CEO of ConeChem Research LLC.
"Urine testing is the standard of industry," Cone said. "Oral fluid testing is as accurate as the urine test, and is easily accessible, not embarrassing for the employee and non-invasive."
Cone explained that saliva testing for drug abuse is a growing trend in the workplace. According to Cone, the United States Department of Health and Human Services is currently developing guidelines for introducing oral fluid testing as a component of government screening.
The Whitman Walker Clinic in Washington, D.C., uses strictly oral testing for HIV. The oral fluid test is also being used in veterinary fields to check doping of animals, like horses. And after the Exxon Valdez oil freighter accident that caused an ecological disaster on the Alaskan coastline, salivary tests have become routine for tug boat captains.